The present invention relates generally to the structure of an electrical cigar lighter especially useful in motor vehicles which consists of a socket having a bimetallic switch in the form of a snap disc and a plug which is plugged into the socket in order to effect heating of a heater element within the plug. More specifically, the invention relates to the type of electrical cigar lighter which comprises a handle or knob on the plug which is axially movably arranged within a jacket and which operates against the action of a return spring. The plug comprises a heated or glowing element against which a cigar or other smoking item is placed for lighting, and the heater element in the plug is surrounded by a dish-shaped contact member or dish by which the heater element is placed in circuit with an electrical circuit within the socket which operates through a current source to effect heating of the heater element.
In a known cigar lighter of the prior art which includes a snap disc for making and breaking circuit contact, contact with the electrical circuit which heats the heater element is made between the dish or dish-shaped contact member of the heater element and the outer edge of the snap disc itself. This type of device is disclosed in German Pat. No. 2329269.
Under cold or unheated conditions, the snap disc of such a device will be placed in a first concave shape and will be located directly in front of the heater element. Due to radiation heat of the heater element, the snap disc absorbs heat and snaps to a second or convex shape. Thus, the contact between the snap disc and the dish of the heater element will be opened and current supply to the heater element will be interrupted.
Because the heat capacity of the snap disc is insignificant, quick interruption of the current supply is possible. Interruption of current is dependent upon the temperature of the heater element. Accordingly, lower dimensioning of the heat conductor forming the heater element is possible. That is, the heat conductor is dimensioned so that the resistance of the conductor will be such that with application of a battery voltage of, for example, 12 volts for a period of between about one or two seconds a temperature of between 600.degree. C. and 1100.degree. C. will be obtained at the heater element. This temperature is sufficient for effecting lighting of a cigarette.
Melting of the heat conductor is prevented by the quick reaction of the snap disc. However, in lighters of this type a disadvantage arises in that the surfaces or points of contact of the electrical circuitry will become dirty and coated with ash residue thereby impeding the making of contact of the electrical circuitry and resulting in uncertain functioning of the lighter.
There is, moreover, the disadvantage that the contact will burn because of thermic overload. In order to insure exact evenness or uniformity at annular surfaces of contact, expensive and precise manufacturing and assembly techniques for the dish member of the heater element and for the snap disc will be required. It has been found that these requirements are a prerequisite for efficient functioning and operation of the snap disc. Because of the manufacturing tolerances of the parts which are required in the socket and the plug, adjustment of the contact compression becomes extremely cumbersome and difficult. The snap disc located in the socket prevents the making of contact with commercially available plugs used for connecting other devices such as vacuum cleaners for automobiles, hand lamps, battery testers, razors or the like.
Accordingly, it is the aim of the present invention to provide a cigar lighter for an automotive vehicle which operates with a more secure and reliable contact-making function with the electrical components of the device while avoiding the disadvantages discussed above. The invention is intended to provide a ligher whose components may be easily and inexpensively manufactured and assembled and which facilitates quick heating of the heater element of the plug.